Translationally controlled tumor protein explained

Translationally controlled tumor protein (TCTP) is a protein that in humans is encoded by the TPT1 gene.^{[1] [2] [3]} TPT1 is mapped to 13q12-q14 on chromosome 13. The human gene contains five introns and six exons, TPT1 contains a promoter with a canonical TATA-box and several promoter elements, which are well-conserved in mammals. The assay with reporter gene exhibits a strong promoter activity comparable to viral promoters.^[4]

TCTP protein is also known as p23,^[5] Fortilin,^[6] and histamine-releasing factor.^{[7] [8]}

TCTP is a multifunctional and highly conserved protein that existed ubiquitously in different eukaryote species and distributed widely in various tissues and cell types.^[9]

TCTP in the human is a growth-related, calcium-binding protein.^[10]

History

Translationally controlled tumor protein was first discovered in 1989 as a cDNA sequence obtained from a human mammary carcinoma cDNA library with proves derived from the translationally controlled, growth-related mouse tumor protein TCTP.^[11] TCTP was originally described as a growth related protein of tumor cells. Its mRNA accumulates in translationally repressed postpolysomal mRNP-complexes.^[12]

Research in 1997 shown that TCTP is not a tumor- or tissue-specific protein, but is expressed ubiquitously from plants to mammals.^{[13] [14] [15] [16]} Later studies show TCTP involvement in a protozoan Trypanosoma brucei.^{[17] [18]}

Characteristics

TCTP is a 20–25 kDa protein abundantly and ubiquitously expressed in the cell. The protein is transcribed in more than 500 different tissues and cell types; hTCTP gene is one of the top 10 most ubiquitously expressed genes in humans by examining 1753 libraries from kinds of tissues,^[19] but differed considerably in their quantity and ratio of expression. The expression is lower in kidney and renal cells. This indicates an extensive transcriptional control and involvement of tissue-specific factors.^[20]

The majority of publications established TCTP to be a cytoplasmic protein but nuclear localisation has also been reported, as well as extracellular activity; however, the process of secretion has not been found.^[20]

Function

The abundance and ubiquity indicate that TCTP may have important primary functions. However, a large number of cellular and biochemical functions have been found since 1980s. Most of these functions can be classified into three groups.

Growth-related

TCTP has properties of a tubulin binding protein that associates with microtubules in a cell cycle-dependent manner.^{[21] [22]}

The transient overexpression of TCTP in HeLa cells prevented them from undergoing etoposide-induced apoptosis.^[6] Expressing TCTP in U2OS (human bone osteosarcoma epithelial cells) protected them from cell death induced by etoposide over various concentrations and durations of exposure. TCTP overexpression inhibited caspase-3-like activity as assessed by the cleavage of fluorogenic substrate.

Expression levels of TCTP were down-regulated at the mRNA and protein levels during tumor suppression and by the activation of p53 and Siah-1 very well known anti-tumor genes.^{[23] [24]} Down-regulation of TCTP can induce tumor reversion, and in combination with some drugs that decrease the level of TCTP and will lead to kill tumor cells.^[25] TCTP knockdown in primary mammary tumor cells, results in increased p53 expression and a decreased number of stem-like cancer cells.^[26]

Reducing TCTP (dTCTP) levels in Drosophila reduces cell size, cell number and organ size, which mimics Drosophila Rheb (dRheb) mutant phenotypes; human TCTP (hTCTP) shows similar biochemical properties compared to dTCTP.

Immunity-related

TCTP caused histamine release from the human basophils of a subpopulation of donors, and this release was dependent on IgE.^{[7] [27]} The expression of TCTP is regulated at two distinct levels, depletion of the ER calcium causes an increase in TCTP mRNA abundance, increased cytosolic calcium concentrations regulate gene expression at the post-transcriptional level.^{[28] [29]}

Downregulation of the protein levels by siRNA in HTR-8/SVneo (Homo sapiens placenta cells) was associated with a reduced cellular calcium-uptake activity and buffering capacity.^[20]

Cancer-related

Translationally controlled tumor protein has a role in tumor reversion and development.^{[30] [31]}

TCTP is a regulator of the cancer stem cell compartment,^[32] the tumor reversion,^{[33] [34]} tumor progression and certain forms of inflammatory diseases.^[7] Moreover, TCTP was described as a pro-survival protein antagonizing BAX function.^[35]

Structure

Sequence alignment of TCTP sequences from more than 30 different species reveals a high degree of conservation over a long period of evolution.^[20]

The solution structure of TCTP from yeast, Schizosaccharomyces pombe has been determined by NMR spectroscopy which indicated that this protein is structurally similar to two small guanine nucleotide-free chaperones, namely Mss4 and Dss4.^[36] TCTP and Mss4/Dss4 are now therefore structurally grouped into one protein superfamily.^[20]

Translationally controlled tumor protein (TCTP) is involved in a wide range of molecular interactions with biological and nonbiological partners of various chemical compositions such as proteins, peptides, nucleic acids, carbohydrates, or small molecules. TCTP is therefore an important and versatile binding platform. Many of these protein–protein interactions have been validated, albeit only few received an in-depth structural characterization. In TCTP/tpt1 - Remodeling Signaling from Stem Cell to Disease, focus is on the structural analysis of TCTP and the review of the available literature regarding its interaction network from a structural perspective.^[37]

The structure of TCTP has a very complex topology composed of three alpha helices, and eleven beta strands arranged in two small beta-sheets, one larger than the other.^[38]

Interactions

TCTP is reported to interact with dozens of other proteins, which relates to its functions in many cellular and biological mechanisms.^[39] TCTP has been shown for example to interact with:

• Apoptosis regulator BAX
• Mcl-1^[40]
• Bcl-xL^[41]

Further reading

• Rasmussen HH, van Damme J, Puype M, Gesser B, Celis JE, Vandekerckhove J . Microsequences of 145 proteins recorded in the two-dimensional gel protein database of normal human epidermal keratinocytes . Electrophoresis . 13 . 12 . 960–9 . December 1992 . 1286667 . 10.1002/elps.11501301199 . 41855774 .
• Hochstrasser DF, Frutiger S, Paquet N, Bairoch A, Ravier F, Pasquali C, Sanchez JC, Tissot JD, Bjellqvist B, Vargas R . Human liver protein map: a reference database established by microsequencing and gel comparison . Electrophoresis . 13 . 12 . 992–1001 . December 1992 . 1286669 . 10.1002/elps.11501301201 . 23518983 .
• MacDonald SM, Rafnar T, Langdon J, Lichtenstein LM . Molecular identification of an IgE-dependent histamine-releasing factor . Science . 269 . 5224 . 688–90 . August 1995 . 7542803 . 10.1126/science.7542803 . 1995Sci...269..688M .
• Rasmussen RK, Ji H, Eddes JS, Moritz RL, Reid GE, Simpson RJ, Dorow DS . Two-dimensional electrophoretic analysis of human breast carcinoma proteins: mapping of proteins that bind to the SH3 domain of mixed lineage kinase MLK2 . Electrophoresis . 18 . 3–4 . 588–98 . 1997 . 9150946 . 10.1002/elps.1150180342 . 37336552 .
• Yoon T, Jung J, Kim M, Lee KM, Choi EC, Lee K . Identification of the self-interaction of rat TCTP/IgE-dependent histamine-releasing factor using yeast two-hybrid system . Archives of Biochemistry and Biophysics . 384 . 2 . 379–82 . December 2000 . 11368327 . 10.1006/abbi.2000.2108 .
• Andersen JS, Lyon CE, Fox AH, Leung AK, Lam YW, Steen H, Mann M, Lamond AI . Directed proteomic analysis of the human nucleolus . Current Biology . 12 . 1 . 1–11 . January 2002 . 11790298 . 10.1016/S0960-9822(01)00650-9 . 14132033 . free .
• Bommer UA, Borovjagin AV, Greagg MA, Jeffrey IW, Russell P, Laing KG, Lee M, Clemens MJ . The mRNA of the translationally controlled tumor protein P23/TCTP is a highly structured RNA, which activates the dsRNA-dependent protein kinase PKR . RNA . 8 . 4 . 478–96 . April 2002 . 11991642 . 1370270 . 10.1017/S1355838202022586 .
• Zhang D, Li F, Weidner D, Mnjoyan ZH, Fujise K . Physical and functional interaction between myeloid cell leukemia 1 protein (MCL1) and Fortilin. The potential role of MCL1 as a fortilin chaperone . The Journal of Biological Chemistry . 277 . 40 . 37430–8 . October 2002 . 12149273 . 10.1074/jbc.M207413200 . free .
• Tuynder M, Susini L, Prieur S, Besse S, Fiucci G, Amson R, Telerman A . Biological models and genes of tumor reversion: cellular reprogramming through tpt1/TCTP and SIAH-1 . Proceedings of the National Academy of Sciences of the United States of America . 99 . 23 . 14976–81 . November 2002 . 12399545 . 137530 . 10.1073/pnas.222470799 . 2002PNAS...9914976T . free .
• Budde IK, Lopuhaa CE, de Heer PG, Langdon JM, MacDonald SM, van der Zee JS, Aalberse RC . Lack of correlation between bronchial late allergic reaction to Dermatophagoides pteronyssinus and in vitro immunoglobulin E reactivity to histamine-releasing factor derived from mononuclear cells . Annals of Allergy, Asthma & Immunology . 89 . 6 . 606–12 . December 2002 . 12487227 . 10.1016/S1081-1206(10)62109-6 .
• Asero R, Tedeschi A, Lorini M, Caldironi G, Barocci F . Sera from patients with multiple drug allergy syndrome contain circulating histamine-releasing factors . International Archives of Allergy and Immunology . 131 . 3 . 195–200 . July 2003 . 12876410 . 10.1159/000071486 . 29623765 .
• Yoneda K, Rokutan K, Nakamura Y, Yanagawa H, Kondo-Teshima S, Sone S . Stimulation of human bronchial epithelial cells by IgE-dependent histamine-releasing factor . American Journal of Physiology. Lung Cellular and Molecular Physiology . 286 . 1 . L174–81 . January 2004 . 12948934 . 10.1152/ajplung.00118.2003 .
• Reuter TY, Medhurst AL, Waisfisz Q, Zhi Y, Herterich S, Hoehn H, Gross HJ, Joenje H, Hoatlin ME, Mathew CG, Huber PA . Yeast two-hybrid screens imply involvement of Fanconi anemia proteins in transcription regulation, cell signaling, oxidative metabolism, and cellular transport . Experimental Cell Research . 289 . 2 . 211–21 . October 2003 . 14499622 . 10.1016/S0014-4827(03)00261-1 .
• Vonakis BM, Sora R, Langdon JM, Casolaro V, MacDonald SM . Inhibition of cytokine gene transcription by the human recombinant histamine-releasing factor in human T lymphocytes . Journal of Immunology . 171 . 7 . 3742–50 . October 2003 . 14500674 . 10.4049/jimmunol.171.7.3742 . free .

Notes and References

1. Gross B, Gaestel M, Böhm H, Bielka H . cDNA sequence coding for a translationally controlled human tumor protein . Nucleic Acids Research . 17 . 20 . 8367 . October 1989 . 2813067 . 334973 . 10.1093/nar/17.20.8367 .
2. MacDonald SM, Paznekas WA, Jabs EW . Chromosomal localization of tumor protein, translationally controlled 1 (TPT1) encoding the human histamine releasing factor (HRF) to 13q12-->q14 . Cytogenetics and Cell Genetics . 84 . 1–2 . 128–9 . Jun 1999 . 10343127 . 10.1159/000015238 . 2024-06-22 . 38129789 .
3. Web site: Entrez Gene: TPT1 tumor protein, translationally-controlled 1.
4. Thiele H, Berger M, Lenzner C, Kühn H, Thiele BJ . Structure of the promoter and complete sequence of the gene coding for the rabbit translationally controlled tumor protein (TCTP) P23 . European Journal of Biochemistry . 257 . 1 . 62–8 . October 1998 . 9799103 . 10.1046/j.1432-1327.1998.2570062.x. free .
5. Böhm H, Benndorf R, Gaestel M, Gross B, Nürnberg P, Kraft R, Otto A, Bielka H . The growth-related protein P23 of the Ehrlich ascites tumor: translational control, cloning and primary structure . Biochemistry International . 19 . 2 . 277–86 . August 1989 . 2479380 .
6. Li F, Zhang D, Fujise K . Characterization of fortilin, a novel antiapoptotic protein . The Journal of Biological Chemistry . 276 . 50 . 47542–9 . December 2001 . 11598139 . 10.1074/jbc.M108954200 . free .
7. MacDonald SM, Rafnar T, Langdon J, Lichtenstein LM . Molecular identification of an IgE-dependent histamine-releasing factor . Science . 269 . 5224 . 688–90 . August 1995 . 7542803 . 10.1126/science.7542803. 1995Sci...269..688M .
8. Web site: UniProt . www.uniprot.org . 30 April 2023.
9. Ren C, Chen T, Jiang X, Wang Y, Hu C . The first characterization of gene structure and biological function for echinoderm translationally controlled tumor protein (TCTP) . Fish & Shellfish Immunology . 41 . 2 . 137–46 . December 2014 . 25193395 . 10.1016/j.fsi.2014.08.030 .
10. Feng Y, Liu D, Yao H, Wang J . Solution structure and mapping of a very weak calcium-binding site of human translationally controlled tumor protein by NMR . Archives of Biochemistry and Biophysics . 467 . 1 . 48–57 . November 2007 . 17897616 . 10.1016/j.abb.2007.08.021 .
11. Gross B, Gaestel M, Böhm H, Bielka H . cDNA sequence coding for a translationally controlled human tumor protein . Nucleic Acids Research . 17 . 20 . 8367 . October 1989 . 2813067 . 10.1093/nar/17.20.8367 . 334973.
12. Chitpatima ST, Makrides S, Bandyopadhyay R, Brawerman G . Nucleotide sequence of a major messenger RNA for a 21 kilodalton polypeptide that is under translational control in mouse tumor cells . Nucleic Acids Research . 16 . 5 . 2350 . March 1988 . 3357792 . 10.1093/nar/16.5.2350 . 338237.
13. Sanchez JC, Schaller D, Ravier F, Golaz O, Jaccoud S, Belet M, Wilkins MR, James R, Deshusses J, Hochstrasser D . Translationally controlled tumor protein: a protein identified in several nontumoral cells including erythrocytes . Electrophoresis . 18 . 1 . 150–5 . January 1997 . 9059837 . 10.1002/elps.1150180127 . 25500696 .
14. Bhisutthibhan J, Pan XQ, Hossler PA, Walker DJ, Yowell CA, Carlton J, Dame JB, Meshnick SR . The Plasmodium falciparum translationally controlled tumor protein homolog and its reaction with the antimalarial drug artemisinin . The Journal of Biological Chemistry . 273 . 26 . 16192–8 . June 1998 . 9632675 . 10.1074/jbc.273.26.16192. free .
15. Yan L, Fei K, Bridge D, Sarras MP . A cnidarian homologue of translationally controlled tumor protein (P23/TCTP) . Development Genes and Evolution . 210 . 10 . 507–11 . October 2000 . 11180799 . 10.1007/s004270000088. 10631675 .
16. Sage-Ono K, Ono M, Harada H, Kamada H . Dark-induced accumulation of mRNA for a homolog of translationally controlled tumor protein (TCTP) in Pharbitis . Plant & Cell Physiology . 39 . 3 . 357–60 . March 1998 . 9588028 . 10.1093/oxfordjournals.pcp.a029377. free .
17. Jojic B, Amodeo S, Bregy I, Ochsenreiter T . Distinct 3' UTRs regulate the life-cycle-specific expression of two TCTP paralogs in Trypanosoma brucei . Journal of Cell Science . 131 . 9 . May 2018 . 29661850 . 5992589 . 10.1242/jcs.206417 .
18. Jojic B, Amodeo S, Ochsenreiter T . The translationally controlled tumor protein TCTP is involved in cell cycle progression and heat stress response in the bloodstream form of Trypanosoma brucei . Microbial Cell . 5 . 10 . 460–468 . August 2018 . 30386790 . 6206406 . 10.15698/mic2018.10.652 .
19. Thompson HG, Harris JW, Wold BJ, Quake SR, Brody JP . Identification and confirmation of a module of coexpressed genes . Genome Research . 12 . 10 . 1517–22 . October 2002 . 12368243 . 10.1101/gr.418402 . 187523 .
20. Bommer UA, Thiele BJ . The translationally controlled tumour protein (TCTP) . The International Journal of Biochemistry & Cell Biology . 36 . 3 . 379–85 . March 2004 . 14687915 . 10.1016/S1357-2725(03)00213-9 .
21. Gachet Y, Tournier S, Lee M, Lazaris-Karatzas A, Poulton T, Bommer UA . The growth-related, translationally controlled protein P23 has properties of a tubulin binding protein and associates transiently with microtubules during the cell cycle . Journal of Cell Science . 112 . 1257–71 . April 1999 . 10085260 . 8. 10.1242/jcs.112.8.1257 .
22. Yarm FR . Plk phosphorylation regulates the microtubule-stabilizing protein TCTP . Molecular and Cellular Biology . 22 . 17 . 6209–21 . September 2002 . 12167714 . 134017 . 10.1128/MCB.22.17.6209-6221.2002 .
23. Cans C, Passer BJ, Shalak V, Nancy-Portebois V, Crible V, Amzallag N, Allanic D, Tufino R, Argentini M, Moras D, Fiucci G, Goud B, Mirande M, Amson R, Telerman A . Translationally controlled tumor protein acts as a guanine nucleotide dissociation inhibitor on the translation elongation factor eEF1A . Proceedings of the National Academy of Sciences of the United States of America . 100 . 24 . 13892–7 . November 2003 . 14623968 . 10.1073/pnas.2335950100 . 283517. 2003PNAS..10013892C . free .
24. Rinnerthaler M, Jarolim S, Heeren G, Palle E, Perju S, Klinger H, Bogengruber E, Madeo F, Braun RJ, Breitenbach-Koller L, Breitenbach M, Laun P . MMI1 (YKL056c, TMA19), the yeast orthologue of the translationally controlled tumor protein (TCTP) has apoptotic functions and interacts with both microtubules and mitochondria . Biochimica et Biophysica Acta (BBA) - Bioenergetics . 1757 . 5–6 . 631–8 . 2016-06-01 . 16806052 . 10.1016/j.bbabio.2006.05.022 . free .
25. Tuynder M, Fiucci G, Prieur S, Lespagnol A, Géant A, Beaucourt S, Duflaut D, Besse S, Susini L, Cavarelli J, Moras D, Amson R, Telerman A . Translationally controlled tumor protein is a target of tumor reversion . en . Proceedings of the National Academy of Sciences of the United States of America . 101 . 43 . 15364–9 . October 2004 . 15489264 . 10.1073/pnas.0406776101 . 523462. 2004PNAS..10115364T . free .
26. Amson R, Pece S, Lespagnol A, Vyas R, Mazzarol G, Tosoni D, Colaluca I, Viale G, Rodrigues-Ferreira S, Wynendaele J, Chaloin O, Hoebeke J, Marine JC, Di Fiore PP, Telerman A . Reciprocal repression between P53 and TCTP . en . Nature Medicine . 18 . 1 . 91–9 . January 2012 . 22157679 . 10.1038/nm.2546 . 22984419 .
27. Bheekha-Escura R, MacGlashan DW, Langdon JM, MacDonald SM . Human recombinant histamine-releasing factor activates human eosinophils and the eosinophilic cell line, AML14-3D10 . Blood . 96 . 6 . 2191–8 . September 2000 . 10.1182/blood.V96.6.2191 . 10979965 .
28. Xu A, Bellamy AR, Taylor JA . Expression of translationally controlled tumour protein is regulated by calcium at both the transcriptional and post-transcriptional level . The Biochemical Journal . 342 . 3 . 683–9 . September 1999 . 10477280 . 1220510 . 10.1042/0264-6021:3420683.
29. Haghighat NG, Ruben L . Purification of novel calcium binding proteins from Trypanosoma brucei: properties of 22-, 24- and 38-kilodalton proteins . Molecular and Biochemical Parasitology . 51 . 1 . 99–110 . March 1992 . 1565142 . 10.1016/0166-6851(92)90205-x.
30. Hsu YC, Chern JJ, Cai Y, Liu M, Choi KW . Drosophila TCTP is essential for growth and proliferation through regulation of dRheb GTPase . Nature . 445 . 7129 . 785–8 . 2007 . 17301792 . 10.1038/nature05528 . 2007Natur.445..785H . 4302643 .
31. Tuynder M, Susini L, Prieur S, Besse S, Fiucci G, Amson R, Telerman A . Biological models and genes of tumor reversion: cellular reprogramming through tpt1/TCTP and SIAH-1 . Proceedings of the National Academy of Sciences of the United States of America . 99 . 23 . 14976–81 . 2002 . 12399545 . 137530 . 10.1073/pnas.222470799 . 2002PNAS...9914976T . free .
32. Amson R, Pece S, Lespagnol A, Vyas R, Mazzarol G, Tosoni D, Colaluca I, Viale G, Rodrigues-Ferreira S, Wynendaele J, Chaloin O, Hoebeke J, Marine JC, Di Fiore PP, Telerman A . Reciprocal repression between P53 and TCTP . Nature Medicine . 18 . 1 . 91–9 . December 2011 . 22157679 . 10.1038/nm.2546 . 22984419 .
33. Tuynder M, Susini L, Prieur S, Besse S, Fiucci G, Amson R, Telerman A . Biological models and genes of tumor reversion: cellular reprogramming through tpt1/TCTP and SIAH-1 . Proceedings of the National Academy of Sciences of the United States of America . 99 . 23 . 14976–81 . November 2002 . 12399545 . 10.1073/pnas.222470799 . 137530. 2002PNAS...9914976T . free .
34. Tuynder M, Fiucci G, Prieur S, Lespagnol A, Géant A, Beaucourt S, Duflaut D, Besse S, Susini L, Cavarelli J, Moras D, Amson R, Telerman A . Translationally controlled tumor protein is a target of tumor reversion . Proceedings of the National Academy of Sciences of the United States of America . 101 . 43 . 15364–9 . October 2004 . 15489264 . 10.1073/pnas.0406776101 . 523462. 2004PNAS..10115364T . free .
35. Susini L, Besse S, Duflaut D, Lespagnol A, Beekman C, Fiucci G, Atkinson AR, Busso D, Poussin P, Marine JC, Martinou JC, Cavarelli J, Moras D, Amson R, Telerman A . TCTP protects from apoptotic cell death by antagonizing bax function . Cell Death and Differentiation . 15 . 8 . 1211–20 . August 2008 . 18274553 . 10.1038/cdd.2008.18 . Laurent Susini . free .
36. Thaw P, Baxter NJ, Hounslow AM, Price C, Waltho JP, Craven CJ . Structure of TCTP reveals unexpected relationship with guanine nucleotide-free chaperones . Nature Structural Biology . 8 . 8 . 701–4 . August 2001 . 11473261 . 10.1038/90415 . 6451004 .
37. Book: Telerman A, Amson R . TCTP/Tpt1 - Remodeling Signaling from Stem Cell to Disease . Structural Insights into TCTP and Its Interactions with Ligands and Proteins . Results and Problems in Cell Differentiation . 64 . 9–46 . 10.1007/978-3-319-67591-6_2. 29149402 . 2017 . 978-3-319-67590-9 .
38. Gao J, Ma Y, Yang G, Li G . Translationally controlled tumor protein: the mediator promoting cancer invasion and migration and its potential clinical prospects . J Zhejiang Univ Sci B . 23 . 8 . 642–654 . August 2022 . 35953758 . 9381325 . 10.1631/jzus.B2100910 .
39. Book: Assrir A, Malard F, Lescop E . TCTP/Tpt1 - Remodeling Signaling from Stem Cell to Disease . Structural Insights into TCTP and Its Interactions with Ligands and Proteins . Results Probl Cell Differ. . Results and Problems in Cell Differentiation . 64 . 9–46 . 2016 . 29149402 . 10.1007/978-3-319-67591-6_2 . 978-3-319-67590-9 .
40. Liu H, Peng HW, Cheng YS, Yuan HS, Yang-Yen HF . Stabilization and enhancement of the antiapoptotic activity of mcl-1 by TCTP . Molecular and Cellular Biology . 25 . 8 . 3117–26 . April 2005 . 15798198 . 10.1128/MCB.25.8.3117-3126.2005 . 1069602.
41. Thébault S, Agez M, Chi X, Stojko J, Cura V, Telerman SB, Maillet L, Gautier F, Billas-Massobrio I, Birck C, Troffer-Charlier N, Karafin T, Honoré J, Senff-Ribeiro A, Montessuit S, Johnson CM, Juin P, Cianférani S, Martinou JC, Andrews DW, Amson R, Telerman A, Cavarelli J . TCTP contains a BH3-like domain, which instead of inhibiting, activates Bcl-xL . Scientific Reports . 6 . 19725 . January 2016 . 26813996 . 10.1038/srep19725 . 4728560. 2016NatSR...619725T .